As the number of mobile users continues to increase, additional licensed band spectrum is needed to support these mobile users. However, licensed band spectrum is not readily available and may be very expensive to acquire. Therefore, it is highly desirable to deploy cellular radio access technologies (RATs) such as, for example, long term evolution (LTE), in newly available spectrum such as television white space (TVWS) or unlicensed bands, which may be collectively referred to as licensed exempt (LE) spectrum.
Operation of the deployed RATs in LE spectrum may be modified to mitigate uncoordinated spectrum usage, as well as to support uplink (UL) and downlink (DL) operation without the need for fixed frequency duplex operation. For example, the spacing between available channels in TVWS may depend on the current location and use of the TVWS by primary users in the vicinity. Furthermore, some areas may only have one TVWS channel available, which may result in having to operate and provide both UL and DL resources on a single TVWS channel. In addition, operation over LE spectrum may be subject to the lower reliability of these channels, (as compared to operation over the licensed bands), and to frequently stop operation on a given channel due to high level interference, the arrival of a primary incumbent, coexistence database decisions, and the like.
Current carrier aggregation (CA) solutions may not be appropriate for these LE bands since the aggregated carriers may rely on the use of licensed secondary component carriers (SCCs), which are reliable and are used by operators with confidence. However, the aggregation scenarios they support may be rather restrictive, (for example, usually implementing DL scenarios where the number of DL SCCs may exceed the number of UL SCCs used in the aggregation).